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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *     http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.giraph.worker;
20  
21  import org.apache.giraph.conf.ImmutableClassesGiraphConfigurable;
22  
23  /**
24   * Observer for worker. The user can subclass and register an observer with the
25   * Giraph framework. The framework will execute methods of the observer at
26   * designated moments of computation on each worker.
27   */
28  public interface WorkerObserver extends ImmutableClassesGiraphConfigurable {
29    /**
30     * Initialize the observer. This method is executed once on each worker before
31     * loading.
32     */
33    void preLoad();
34  
35    /**
36     * Initialize the observer. This method is executed once on each worker after
37     * loading before the first superstep starts.
38     */
39    void preApplication();
40  
41    /**
42     * Execute the observer. This method is executed once on each worker before
43     * each superstep starts.
44     *
45     * @param superstep number of superstep
46     */
47    void preSuperstep(long superstep);
48  
49    /**
50     * Execute the observer. This method is executed once on each worker after
51     * each superstep ends.
52     *
53     * @param superstep number of superstep
54     */
55    void postSuperstep(long superstep);
56  
57    /**
58     * Finalize the observer. This method is executed once on each worker after
59     * the last superstep ends before saving.
60     */
61    void postApplication();
62  
63    /**
64     * Finalize the observer. This method is executed once on each worker after
65     * saving.
66     */
67    void postSave();
68  }